Diesel variant

Newer diesel is much cleaner

Common rail injectors
Egr
Dpf
Euro 5

these are the few technology which dramatically reduced those toxic element. If you stand behind an old diesel and modern Diesel engine, you will realized how much cleaner the exhaust be. Some manufacturer even place a white cloth just to prove the cleanliness. However, this may not be true if you pedal to the metal often.

Maintenance are pretty much mainstream and manufacturer have come up with different technologies to combat the issue. Soot mostly collected by the dpf system. Modern cars would burn off the soot in the dpf to minimize clog. If there's sever issues with the dpf unit, most service center can clean the unit with ease. Engine requires minimal maintenance. Components which clean off the exhaust gases needs a bit of care. But not as difficult as many would assume.